Came back from holiday today to be greeted by the usual tube **** up.
Signal failure on the Victoria line. Something that I hadn't wondered
before is how exactly can you have a signal failure on a line thats
controlled by ATO via a leaky feeder cable? The light signals are
AFAIK there simply as extra information for drivers and arn't really
required anyway so if one fails so what? The train is control by the
ATO cable signals , not a cluster of coloured lights in the tunnel. Or
is "signal failure" just an LU catch all phrase for a computer
failure?

B2003

On Aug 22, 8:05 pm, Boltar wrote:
Came back from holiday today to be greeted by the usual tube **** up.
Signal failure on the Victoria line. Something that I hadn't wondered
before is how exactly can you have a signal failure on a line thats
controlled by ATO via a leaky feeder cable? The light signals are
AFAIK there simply as extra information for drivers and arn't really
required anyway so if one fails so what? The train is control by the
ATO cable signals , not a cluster of coloured lights in the tunnel. Or
is "signal failure" just an LU catch all phrase for a computer
failure?

B2003


I always thought that it kind of meant "track/circuit failure
resulting in signals going red".

I suppose signals must be able to fail in some sense, but I don't
think signal failures often mean anything other than signals doing
their job correctly when something else fails.

Boltar wrote:
Came back from holiday today to be greeted by the usual tube **** up.
Signal failure on the Victoria line. Something that I hadn't wondered
before is how exactly can you have a signal failure on a line thats
controlled by ATO via a leaky feeder cable? The light signals are
AFAIK there simply as extra information for drivers and arn't really
required anyway so if one fails so what? The train is control by the
ATO cable signals , not a cluster of coloured lights in the tunnel. Or
is "signal failure" just an LU catch all phrase for a computer
failure?

AFAIK the victoria is not computerised ATO. I works using mechanical
odometry and still relies on a block signalling system. It outdates
viable computers by a decade or two.

I could be wrong...

Tony

On Aug 22, 8:05 pm, Boltar wrote:
The train is control by the ATO cable signals , not a cluster of coloured
lights in the tunnel. Or is "signal failure" just an LU catch all phrase for
a computer failure?

Yes. For reasons I can't remember, there are only something like 5 or
6 possible phrases they'll use to explain delays to the public.
"Signal failure" is very broad and could mean any kind of signalling/
ATO/points/etc problem. "Passenger action" is another one.

U

--
http://londonconnections.blogspot.com/
A blog about transport projects in London

Boltar wrote:
Came back from holiday today to be greeted by the usual tube **** up.
Signal failure on the Victoria line. Something that I hadn't wondered
before is how exactly can you have a signal failure on a line thats
controlled by ATO via a leaky feeder cable? The light signals are
AFAIK there simply as extra information for drivers and arn't really
required anyway so if one fails so what? The train is control by the
ATO cable signals

Haven't you just answered your own question?

On Aug 22, 8:52 pm, Tony Chung tony@invalid wrote:
Boltar wrote:
Came back from holiday today to be greeted by the usual tube **** up.
Signal failure on the Victoria line. Something that I hadn't wondered
before is how exactly can you have a signal failure on a line thats
controlled by ATO via a leaky feeder cable? The light signals are
AFAIK there simply as extra information for drivers and arn't really
required anyway so if one fails so what? The train is control by the
ATO cable signals , not a cluster of coloured lights in the tunnel. Or
is "signal failure" just an LU catch all phrase for a computer
failure?

AFAIK the victoria is not computerised ATO. I works using mechanical
odometry and still relies on a block signalling system. It outdates
viable computers by a decade or two.

I could be wrong...

Tony

You are correct there.
The only line that use computer and non-mechanical (SSI/Relay etc)
signalling is the Central. The Jubilee does too between Green Park
and Stratford, but still uses Train Stops.
The other lines that have computers operating mechanical signalling
equipment are Bakerloo and the Circle Signalling centre (Stanmore-
Charing Cross and Wembley Park-Aldgate (Minories/Aldgate East)) and
the Piccadilly line north of Wood Green.

As to the term Signal Failure. This is a blanket term for any failure
of the signalling system (except where it is multi-site caused by the
same problem, where it is know as a Signalling System Failure). It is
mainly used where the failure is down to the Infraco or Network Rail.
Where LUL are at fault, such as a SPAD or Wrong Signal Lowered and
Accepted, it is put over as a Signalling Problem.

Are the signals that are normally found on the upper left side of the tunnel
entrances at Victoria line stations actually starter signals or are they
platform repeaters? I notice that the stations do not appear to have
track-level starters, execpt for areas where there are points, such as at
Victoria.

I realise that the various equipments differ, but I it seems that signal
aspects on the Victoria line are the same as those on the Central line.
These include a danger aspect, an aspect allowing trains on code to proceed
and a clear aspect for all trains.

In any event, I notice that many drivers on the Central and Victoria lines
prefer to wait until they get a full clear before closing up and proceeding,
although some will depart when the signal indicated clear for coded trains.
Why is that?

wrote:
Are the signals that are normally found on the upper left side of the
tunnel entrances at Victoria line stations actually starter signals
or are they platform repeaters? I notice that the stations do not
appear to have track-level starters, execpt for areas where there are
points, such as at Victoria.

I realise that the various equipments differ, but I it seems that
signal aspects on the Victoria line are the same as those on the
Central line. These include a danger aspect, an aspect allowing
trains on code to proceed and a clear aspect for all trains.

In any event, I notice that many drivers on the Central and Victoria
lines prefer to wait until they get a full clear before closing up
and proceeding, although some will depart when the signal indicated
clear for coded trains. Why is that?

The platform headwall corner signals are "true" starters. A Vic line train
running in usual ATO mode will not normally pass a red signal (white aspect
shown when an ATO train can pass, but train in manual cannot). The same
thing is true where signals are ptrovided away from stations (usually
confliction point protection or where there are more than one route from the
signal). Headway posts are not intended to be stopped at by non ATO trains.

The corner signals realy become significant in degraded mode where manual
driving is necessary or if non ATO equipped works trains are running on the
line outside a possession (not sure if that is still allowed).

The existing Vic line signalling (due for replacement in the near future)
uses coded track circuits with a very restricted number of codes (3 running
codes for 2 train running speeds and 1 "code" only identified as part of the
signalling system).

Being pedantic the Vic Line mixes ATO with ATP (automatic train
protection) - the latter is, in very broad terms, the auto equivalent of
the fail safe signalling system.

Peter
--
Peter & Elizabeth Corser
Leighton Buzzard, UK

On Wed, 22 Aug 2007 13:17:07 -0700, Mr Thant
wrote:

On Aug 22, 8:05 pm, Boltar wrote:
The train is control by the ATO cable signals , not a cluster of coloured
lights in the tunnel. Or is "signal failure" just an LU catch all phrase for
a computer failure?

Yes. For reasons I can't remember, there are only something like 5 or
6 possible phrases they'll use to explain delays to the public.
"Signal failure" is very broad and could mean any kind of signalling/
ATO/points/etc problem. "Passenger action" is another one.

"Signal failure" is at least meaningful (though posibly slightly
misleading). The phrase "passenger action" deserves to be sent to the
same hell to which I would banish all management speak. ("There's no I
in team" -- "Unless you're French", I always reply.)

On Aug 22, 9:42 pm, "John Rowland"
wrote:
Haven't you just answered your own question?

No. If it was a signal failure why couldn't the trains still run? If
it was an ATO failure then how could anything run?

B2003